FIG. 1 shows a conventional ink-jet recording head. FIG. 1(A) is a diagram showing the outline of a configuration of individual electrodes 102 and their periphery of an ink-jet recording head 100. FIG. 1(B) shows the outline of a configuration of the ink-jet recording head 100 of FIG. 1(A) viewed in the direction indicated by the arrows A-A. Normally, the ink-jet recording head 100 includes numerous nozzles 107 so as to form characters or images by numerous ink dots, while only two head parts are shown in FIGS. 1(A) and (B).
The ink-jet recording head 100 includes an ink supply system including ink chambers 106, a pressure-generating system including piezoelectric elements 103 generating pressure inside the ink chambers 106, and a nozzle plate 108 having nozzles 107 spraying ink droplets in accordance with the pressure inside the ink chambers 106.
The ink supply system includes a common ink channel 113 supplying ink from an ink tank not shown in the drawings and ink supply channels 112 connecting the common ink channel 113 to each ink chamber 106.
The pressure-generating system includes a diaphragm 104 forming the wall of one side of each ink chamber 106, the piezoelectric elements 103 provided on the diaphragm 104, and the individual electrodes 102 provided on the piezoelectric elements 103. The diaphragm 104, which is formed of a conductive material such as Cr or Ni—Cr, serves also as a common electrode and is provided to cover all the ink chambers 106. The diaphragm 104, however, is joined firmly to the peripheral wall part of each ink chamber 106, and oscillates separately for each ink chamber 106. Oscillation isolation is provided so that no adjacent ink chambers 106 are affected by each other's oscillation.
Each ink chamber 106 is provided with the corresponding individual piezoelectric element 103 and individual electrode 102. The piezoelectric element 103, when supplied with an electric charge between the individual electrode 102 and the diaphragm 104 (common electrode), is displaced proportional to the amount of charge. Due to this displacement, the diaphragm 104 is bent to generate pressure inside the ink chamber 106, thereby spraying ink from the nozzle 107 so that recording such as printing is performed on a recording medium. At this point, the charge is supplied to each piezoelectric element through an individual driving signal 114 from a printer main body (not shown in the drawings) via the corresponding individual electrode 102 and the diaphragm 104.
In the ink-jet recording head 100, the nozzles 107 are positioned to oppose the diaphragm 104 with the ink chambers 106 being formed therebetween.
In the ink-jet recording head 100, the individual electrodes 102, the diaphragm 104, and the piezoelectric elements 103 are required to be formed into extremely thin films using metallic and piezoelectric materials. For this purpose, recently, thin-film deposition technologies such as sputtering and etching employed in the field of semiconductor manufacture have been used to manufacture ink-jet recording heads.
A brief description will be given, with reference to FIG. 1(C) showing a layer structure of the ink-jet recording head 100, of a manufacturing process thereof. FIG. 1(C) shows the outline of a configuration of the ink-jet recording head 100 of FIG. 1(B) viewed in the direction indicated by the arrows B-B.
The ink-jet recording head 100 is manufactured by laminating a plurality of layers (films) on a magnesium oxide (MgO) substrate 101, for instance. These layers are processed into necessary shapes and laminated successively so as to be formed finally into the ink-jet recording head 100. In FIG. 1, reference numeral 101 denotes the substrate, which is removed by etching in the final step of manufacturing but, in some cases, is partially preserved for reinforcing the ink-jet recording head 100. The preserved part of the substrate 101 is shown in the ink-jet recording head 100 shown in FIG. 1.
If a thin-film deposition technology is employed in manufacturing the ink-jet recording head 100, a metal thin film can be formed on the substrate 101 one at a time by sputtering, and a layer having a desired pattern can be formed one at a time by performing etching after a resist process. Further, a plurality of layers to be processed into the same shape are processed at the same time in a single etching process after all the layers are laminated. Thereby, the ink-jet recording head 100 can be manufactured efficiently.
In the ink-jet recording head 100 shown in FIG. 1(C), the individual electrode 102 and the piezoelectric element 103 are required to have substantially the same shape. Therefore, in terms of manufacturing efficiency, an individual electrode formation layer and a piezoelectric element formation layer are etched, after being successively formed, so that the individual electrode 102 and the piezoelectric element 103 are simultaneously formed.
When the ink-jet recording head 100 is manufactured by using the thin-film deposition technology as described above, however, the piezoelectric element 103 provided to bend the diaphragm 104 also exists under an individual electrode lead-out part 102A. Therefore, when the driving signal 114 is supplied to the piezoelectric element 103, the piezoelectric element 103 is also displaced unnecessarily under the lead-out part 102A. When the piezoelectric element 103 is thus displaced where the piezoelectric element 103 is not required to, the ink supply channel 112 is deformed, for instance, so that the particle characteristic of ink sprayed from the nozzle 117 is adversely affected. Further, it becomes difficult to reduce the cost of the driver, which should include capacitance for driving the piezoelectric element 103 where the piezoelectric element 103 is not required to be driven. Moreover, the individual electrode lead-out part 102A, which is formed to be extremely thin, for instance, 0.2 μm, and narrow in width, may generate heat or be broken, and thus is of questionable reliability.
Accordingly, a principal object of the present invention is to provide an ink-jet recording head having no piezoelectric element in a part where no piezoelectric element is required and including an individual electrode lead-out part having a cross section allowing smooth power supply, and a method of manufacturing the same.